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><A
NAME="MONITORING-PS"
>27.1. Standard Unix Tools</A
></H1
><P
>   On most Unix platforms, <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> modifies its
   command title as reported by <TT
CLASS="COMMAND"
>ps</TT
>, so that individual server
   processes can readily be identified.  A sample display is

</P><PRE
CLASS="SCREEN"
>$ ps auxww | grep ^postgres
postgres   960  0.0  1.1  6104 1480 pts/1    SN   13:17   0:00 postgres -i
postgres   963  0.0  1.1  7084 1472 pts/1    SN   13:17   0:00 postgres: writer process
postgres   965  0.0  1.1  6152 1512 pts/1    SN   13:17   0:00 postgres: stats collector process
postgres   998  0.0  2.3  6532 2992 pts/1    SN   13:18   0:00 postgres: tgl runbug 127.0.0.1 idle
postgres  1003  0.0  2.4  6532 3128 pts/1    SN   13:19   0:00 postgres: tgl regression [local] SELECT waiting
postgres  1016  0.1  2.4  6532 3080 pts/1    SN   13:19   0:00 postgres: tgl regression [local] idle in transaction</PRE
><P>

   (The appropriate invocation of <TT
CLASS="COMMAND"
>ps</TT
> varies across different
   platforms, as do the details of what is shown.  This example is from a
   recent Linux system.)  The first process listed here is the
   master server process.  The command arguments
   shown for it are the same ones used when it was launched.  The next two
   processes are background worker processes automatically launched by the
   master process.  (The <SPAN
CLASS="QUOTE"
>"stats collector"</SPAN
> process will not be present
   if you have set
   the system not to start the statistics collector.)  Each of the remaining
   processes is a server process handling one client connection.  Each such
   process sets its command line display in the form

</P><PRE
CLASS="SCREEN"
>postgres: <TT
CLASS="REPLACEABLE"
><I
>user</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>database</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>host</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>activity</I
></TT
></PRE
><P>

  The user, database, and (client) host items remain the same for
  the life of the client connection, but the activity indicator changes.
  The activity can be <TT
CLASS="LITERAL"
>idle</TT
> (i.e., waiting for a client command),
  <TT
CLASS="LITERAL"
>idle in transaction</TT
> (waiting for client inside a <TT
CLASS="COMMAND"
>BEGIN</TT
> block),
  or a command type name such as <TT
CLASS="LITERAL"
>SELECT</TT
>.  Also,
  <TT
CLASS="LITERAL"
>waiting</TT
> is appended if the server process is presently waiting
  on a lock held by another session.  In the above example we can infer
  that process 1003 is waiting for process 1016 to complete its transaction and
  thereby release some lock.
  </P
><P
>   If you have turned off <A
HREF="runtime-config-statistics.html#GUC-UPDATE-PROCESS-TITLE"
>update_process_title</A
> then the
   activity indicator is not updated; the process title is set only once
   when a new process is launched.  On some platforms this saves a measurable
   amount of per-command overhead;  on others it's insignificant.
  </P
><DIV
CLASS="TIP"
><BLOCKQUOTE
CLASS="TIP"
><P
><B
>Tip: </B
>  <SPAN
CLASS="PRODUCTNAME"
>Solaris</SPAN
> requires special handling. You must
  use <TT
CLASS="COMMAND"
>/usr/ucb/ps</TT
>, rather than
  <TT
CLASS="COMMAND"
>/bin/ps</TT
>. You also must use two <TT
CLASS="OPTION"
>w</TT
>
  flags, not just one. In addition, your original invocation of the
  <TT
CLASS="COMMAND"
>postgres</TT
> command must have a shorter
  <TT
CLASS="COMMAND"
>ps</TT
> status display than that provided by each
  server process.  If you fail to do all three things, the <TT
CLASS="COMMAND"
>ps</TT
>
  output for each server process will be the original <TT
CLASS="COMMAND"
>postgres</TT
>
  command line.
  </P
></BLOCKQUOTE
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